As the orbit of Comet Hale-Bopp (C/1995 O1) brings it
closer to the Sun in late March, NASA and agency-supported
scientists will study the large and bright comet using sounding
rockets, spacecraft and ground-based observations. Using NASA's
Hubble Space Telescope, Hale-Bopp's nucleus was measured at
roughly three to four times larger than that of comet Halley (six
miles in diameter), making it one of the largest comets ever
observed. Researchers are studying Hale-Bopp to better
understand comets, primitive bodies of loosely-packed ice and
dust that many scientists consider the best-preserved remnants of
the early solar system.

Other agency activities, including a media day for
coverage of the sounding rocket launches, and special Internet
home pages for posting images obtained by NASA missions as well
as amateur astronomers, are outlined below with points of contact
and other relevant information.

Sounding Rocket Campaign

The Wallops Flight Facility (WFF), Wallops Island, VA,
will conduct four sounding rocket launches starting March 24
through April 5. The missions will be launched for NASA by the
U.S. Navy at the White Sands Missile Range (WSMR), NM. The
payloads, launched on two-stage Black-Brant IX rockets, will
observe the comet in the ultraviolet wavelengths of light for
about five minutes before returning to Earth. The payloads will
be recovered following a parachute descent at White Sands.
Images of the sounding rocket activity at WSMR will be posted to
the Internet at: http://www.wff.nasa.gov/~web/comet.html.

WFF and WSMR will host a media day at White Sands Missile
Range from noon to 4 p.m. MST, March 24. Dr. Alan Hale, co-
discoverer of the comet, will be at the site to speak to
reporters. Media also are invited to cover the 8:15 p.m. MST
launch. For clearance to visit White Sands, call the White Sands
Public Affairs Office (PAO) at 505/678-1134. For more
information on the sounding rocket campaign, call WFF PAO at
757/824-1579.

Ulysses spacecraft

The joint NASA/European Space Agency Ulysses spacecraft,
now in solar orbit, will study what happens to comets as they are
exposed to different solar wind conditions at various solar
latitudes. Hale-Bopp is about to enter the Sun's lower latitude
zone, where solar wind (a continuous outflow of charged particles
streaming from the Sun in all directions at a million miles per
hour) is disturbed compared with the equatorial regions. Dramatic
changes in the comet's plasma tail are expected to occur at these
lower celestial latitudes.

A related observing program, called "Ulysses Comet Watch,"
a collaboration between the Jet Propulsion Laboratory (JPL),
Pasadena, CA, and the University of Colorado, will provide images
from more than 200 amateur observers around the world. These
images will be posted on the Ulysses Comet Watch home page on the
Internet at http://lasp.colorado.edu/ucw/. Observations
will continue to be posted after the comet makes its closest
approach to the Sun on April 1.

Hubble Space Telescope

NASA's Hubble Space Telescope has made a series of
observations of the comet, particularly the nucleus, since
September 1995. Hubble cannot observe Hale-Bopp during the next
few months because the comet is too close to the Sun -- Hubble's
sensitive detectors could be damaged if pointed in that
direction. The last observation was made on Oct. 18, 1996, and
the next possible opportunity will be this autumn.

Dr. Harold Weaver will publish the results of his
observations with Hubble in the March 28 issue of Science
magazine. For more information, contact the Space Telescope
Science Institute (STScI), Baltimore, MD, at 410/338-4514.
Images already obtained by Hubble are available from the Internet
at http://oposite.stsci.edu/pubinfo/PR/95/41.html.

Other NASA Comet Investigations

NASA's Polar spacecraft will make observations of Hale-
Bopp using ultraviolet and visible imaging instruments. For more
information call the Goddard Space Flight Center, PAO, Greenbelt,
MD, at 301/286-0697. Images obtained by Polar will be posted to
the Internet site at:
http://pao.gsfc.nasa.gov/gsfc/spacesci/pictures/spacepic.htm.
Scientists have been using NASA's Infrared Telescope Facility,
Mauna Kea, HI, to observe Hale-Bopp in the infrared region of the
spectrum. Their observations will be made through Hale-Bopp's
perihelion and continue until summer. For more information call
NASA Headquarters at 202/358-1547.

NASA also will fly a mid-deck experiment on the Space
Shuttle Discovery's STS-85 mission in July. The experiment is
the Southwest Ultraviolet Imaging System, designed to complement
the capabilities of the 5-10 minute sounding rocket flights by
observing the comet more extensively during the Shuttle's 11-day
mission. For more information call NASA Headquarters at 202/358-
1547.

In addition, NASA and the National Science Foundation are
collaborating on ground-based observations and analyses of Hale-
Bopp. For information, contact NASA Headquarters at 202/358-
1547.

JPL "Comet Chasers: On the Trail of a Comet" Public Event

JPL will host a public event called "Comet Chasers: On the
Trail of a Comet" on Friday, April 11, at JPL. The event is co-
sponsored by the Galileo and Stardust projects. Galileo, which
is touring the Jovian system, observed the 1994 Comet Shoemaker-
Levy 9 impact on Jupiter. Stardust will launch in 1999, capture
samples of comet dust from the Comet Wild-2 and return them to
Earth for study. Activities will include a comet viewing session
(weather permitting), and a round-table discussion of the study
of comets and NASA's role in comet studies, featuring David Levy,
co-discoverer of Comet Shoemaker-Levy 9, Dr. Don Yeomans of JPL,
and Dr. Alan Hale and Thomas Bopp, co-discoverers of Comet Hale-
Bopp. The panelists also will discuss NASA's Stardust mission to
Comet Wild-2 in 2004. For more information, call 818/354-5011.

Amateur astronomers who have images of Hale-Bopp in
electronic file format are invited to post their pictures to a
NASA web page at URL: http://comet.hq.nasa.gov/.
Prior to posting, one must first register following the prompts
on that page.

Comet researchers are available for interviews, both in
person and via satellite, at NASA Headquarters as well as GSFC,
WFF, JPL and STScI and other Centers. Contact the respective
Public Affairs Offices for further information.